Foreigner here (French). Why is Tin funny? It stands for the small metal box with food inside, like Can, doesn't it?

'Does what it says on the tin' is a common phrase in English, usually applied to mean a product is simple and effective. I guess it's meant to contrast against the marketing hyperbole that you often read on tin labels.

I saw another suggestion elsewhere for 'tldr'

I like that very much. It accurately describes my use case for bropages. And - getting back to some cultural neutrality - you can explain its meaning just fine without referring to the recent usage context in "the" Internet.

The perfect answer to 'rtfm'!